Synthesis and antifungal activity of diverse C-2 pyridinyl and pyridinylvinyl substituted quinolines

Article abstract of DOI:10.1016/j.bmc.2012.08.036

Diverse 2-pyridinyl quinolines 6-12 and 2-pyridinilvinyl quinolines 13-17 were prepared using a straightforward synthesis based on the BiCl ₃-catalyzed multicomponent imino Diels-Alder (imino DA) reaction or a novel tandem imino DA/catalytic tetrahydroquinoline ring oxidation/Perkin condensation sequential process. All members of the series showed activities against dermatophytes and some of them possessed a broad spectrum of action. 2-(Pyridin-4-yl)quinoline 9 and 2-(2-pyridin-4-yl)vinyl)quinoline 16 showed the best MIC₈₀ and MIC₅₀ against the clinically important fungi Candida albicans and non-albicans Candida species. In turn, 6-ethyl-2-(pyridin-2-yl)quinoline 6 showed the best properties against standardized as well as clinical strains of Cryptococcus neoformans.

Full text of DOI:10.1016/j.bmc.2012.08.036

Bioorganic & Medicinal Chemistry 20 (2012) 6506–6512
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and antifungal activity of diverse C-2 pyridinyl and pyridinylvinyl
substituted quinolines
a,
⇑
b
c
c
Vladimir V. Kouznetsov , Carlos M. Meléndez Gómez , Marcos G. Derita , Laura Svetaz ,
d
c
Esther del Olmo , Susana A. Zacchino
a
Laboratorio de Química Orgánica y Biomolecular, Escuela de Química, Universidad Industrial de Santander, A.A. 678, Bucaramanga, Colombia
Grupo de Investigación en Compuestos Heterocíclicos, Programa de Química, Facultad de Ciencias Básicas, Universidad del Atlántico, A.A. 1890, Barranquilla, Colombia
Farmacognosia, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, (2000) Rosario, Argentina
Departamento de Química Farmacéutica, Facultad de Farmacia, Universidad de Salamanca, Campus Unamuno, s/n, 37007 Salamanca, Spain
b
c
d
a r t i c l e i n f o
a b s t r a c t
Article history:
Diverse 2-pyridinyl quinolines 6–12 and 2-pyridinilvinyl quinolines 13–17 were prepared using a
Received 30 May 2012
Revised 6 August 2012
Accepted 13 August 2012
Available online 30 August 2012
3
straightforward synthesis based on the BiCl -catalyzed multicomponent imino Diels–Alder (imino DA)
reaction or a novel tandem imino DA/catalytic tetrahydroquinoline ring oxidation/Perkin condensation
sequential process. All members of the series showed activities against dermatophytes and some of them
possessed a broad spectrum of action. 2-(Pyridin-4-yl)quinoline 9 and 2-(2-pyridin-4-yl)vinyl)quinoline
1
6 showed the best MIC80 and MIC50 against the clinically important fungi Candida albicans and
Keywords:
non-albicans Candida species. In turn, 6-ethyl-2-(pyridin-2-yl)quinoline 6 showed the best properties
against standardized as well as clinical strains of Cryptococcus neoformans.
Ó 2012 Elsevier Ltd. All rights reserved.
2
-Pyridinyl and 2-pyridinylvinyl quinoline
derivatives
Antifungal agents
Imino Diels–Alder reaction
Diversity-oriented synthesis
1
. Introduction
Herein, we report the synthesis of a new series of diverse
2
-pyridinyl and pyridinylvinyl quinoline derivatives related to
In the last years, fungi have emerged as major cause of human
quinolines that have previously showed interesting biological
1
1–16
infections especially among immunocompromised hosts having an
activities.
These C2-substituted quinolines were tested for
1
enormous impact on morbidity and mortality. Although there are
antifungal properties against standardized as well clinically impor-
tant fungi including Cryptococcus neoformans, several species of
Candida and Aspergillus genus, and dermatophytes.
diverse available drugs for the treatment of systemic and superfi-
cial mycoses, they are not completely effective for their eradica-
2
,3
tion. In addition, they all possess a certain degree of toxicity
4
and quickly develop resistance due to the large-scale use. There
2
2
. Results and discussion
.1. Chemistry
is, therefore, an urgent need for new antifungal chemical structures
alternatives to the existing ones.5
Compounds with a quinoline skeleton are considered attractive
scaffolds to develop new antifungal agents. So, 8-hydroxyquino-
2
-Pyridinyl quinolines 6–12 were prepared using a straightfor-
ward synthesis based on the BiCl -catalyzed multicomponent
imino Diels–Alder (imino DA) reaction among substituted anilines
, ethyl vinyl ether 2 and isomeric - and b- or -pyridinecarbox-
lines, 2-aryl- or styryl- quinolines showed potent antifungal
activity.6–9 These quinoline derivatives are low molecular weight
3
heterocyclic aromatic molecules easily obtained by straightfor-
ward syntheses. The course of our ongoing screening program for
new biologically important N-heterocycles is based on the ‘‘one-
pot’’ imino Diels–Alder reaction, using commercially available aryl-
amines and aldehydes as principal starting materials, that allows
1
a
c
aldehydes 3 in refluxing MeCN. These quinolines were obtained as
stable solids in 35–47% yield after their chromatography purifica-
tion (Scheme 1, Route a).
The syntheses of the 2-(pyridinylvinyl)quinoline analogs 13–17
were accomplished through a novel tandem imino DA/catalytic
tetrahydroquinoline ring oxidation/Perkin condensation sequential
process (Scheme 1, Route b), which starts with a cycloaddition
reaction between substituted anilines 1 and ethyl vinyl ether 2.
This first step was produced by the o-phthalic acid-catalyzed
high degrees of structural diversification, in the construction of
diverse molecular quinoline library.10
⇑
Corresponding author.
E-mail address: kouznet@uis.edu.co (V.V. Kouznetsov).
0
968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.08.036

V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
6507
R2
R2
H
N
NH
2
Me
N
H
Me
o-C
6
H
4
(COOH)
2
Pd/C
O
Me
+
2
R
1
R
2
MeOH(ac)
R1
MeOH R1
1
4a-i
5
a-i
Route b
O
Route a
O
O
BiCl
CH
3
CN
Me
4,5 R1 = H, Me, MeO, F, Cl;
= H, Cl
2
Ac O
H
3
N
N
R
2
α-, β-, γ-Py
3
3
R2
R
2
N
N
N
N
R1
6-12
R
1
13-17
Scheme 1.
Table 2 summarizes the minimum concentration of compounds
that completely inhibited the growth (MIC100) of nine opportunis-
tic pathogenic fungi including yeasts (Candida albicans, C. neofor-
mans, Saccharomyces cerevisiae), hialohyphomycetes (Aspergillus
spp.) as well as dermatophytes (Microsporum and Trichophyton
spp.). In addition, the minimum concentration of compound that
kills the fungi (Minimum Fungicide Concentration, MFC) was re-
corded in Table 2. The structure of each quinoline derivative was
included in Table 2 too, for the sake of an easier analysis of results.
From results of Table 2, it is clearly observed that seven
compounds6, 9, 10, 13, 14, 16 and 17 show the broadest spectrum
of action inhibiting the whole fungal panel. Although the activity is
moderate compared to the standard drugs, it is important to
highlight that they inhibit (and in some cases kill) strains of the
clinically important fungi C. neoformans and C. albicans.
Table 1
Physico-chemical data of 2-pyridinylquinolines 6–12 and (E)-2-(pyridinylvinyl)quin-
olines 13–17
Compd Group
R
1
R
2
N
MF
MW
Mp
°C)
Yield
(%)
(
6
7
8
9
A
A
A
A
C
2
H
5
H
H
H
H
a
b
b
c
C
C
C
C
16
14
14
14
H
H
H
H
14
N
2
234.30 148–
50
240.69 150–
52
224.23 162–
64
206.24 148–
50
220.27 82–84
240.69 138–
40
240.69 176–
78
42
36
38
40
1
Cl
F
9
9
ClN
2
1
FN
2
1
H
10
N
2
2
1
1
1
0
1
A
A
CH
Cl
3
H
H
c
c
C
C
15
H
H
12
N
47
39
14
9
ClN
2
2
1
1
2
A
H
Cl
c
C
14
H
9
ClN
35
Regarding C. neoformans this fungus remains an important life-
threatening complication for immunocompromised hosts, particu-
larly for patients who have undergone transplantation of solid
organs. Therefore, new compounds acting against this fungus are
1
1
1
3
4
B
B
F
H
H
H
a
b
C
C
16
H
H
11FN
12
2
250.27 oil
232.28 173–
47
45
16
N
2
1
75
266.72 177–
79
232.28 169–
72
266.72 180–
81
1
1
1
5
6
7
B
B
B
Cl
H
H
H
H
b
c
c
C
C
C
16
16
16
H
H
H
11ClN
2
40
43
41
1
9,20
highly welcome.
1
12 2
N
Respecting species of the Candida genus, it is known that they
are among the leading causes of nosocomial blood stream infec-
tions worldwide and, although C. albicans was in the past the usual
species associated to invasive infections, at present non-albicans
Candida spp. such as Candida tropicalis, Candida glabrata, Candida
parapsilopsis, Candida krusei and others, comprise more than half
1
Cl
11ClN
2
1
MF: Molecular formula; MW: Molecular weight; Mp: Melting point.
2
1
of the isolates of candidiasis in human beings.
domino Povarov reaction in aqueous methanol that conducted to
the formation of the 4-ethyloxy-2-methyl-1,2,3,4-tetrahydroquin-
oline derivatives 4a–i. Their catalytic aromatization (10% Pd/C)
allowed to prepare the corresponding 2-methylquinolines 5 substi-
tuted at the arene part of quinoline ring. The last step of the syn-
thetic scheme to 2-pyridinylvinyl quinolines 13–17 was a Perkin
condensation between compound 5 and pyridinecarboxaldehydes
Compounds6, 9, 10, 13, 14, 16 and 17 showed moderate to low
activities against all fungi tested (Table 2). However, it is important
to take into account that these MIC values refer to the minimum
concentration necessary to inhibit 100% of the fungal growth. If,
as recommended by CLSI, less stringent end-points such as MIC80
or MIC50 (the minimum concentration of compounds that inhibit
80 and 50% of growth, respectively) are determined, lower
minimum inhibitory concentrations for each compound would be
obtained opening the possibilities of detecting interesting hits. In
addition, the application of less stringent end-points has been
showed to consistently represent the in vitro activity of com-
pounds and many times provide a better correlation with other
measurements of antifungal activity such as the Minimum Fungi-
1
1
3
2
(reflux in Ac O). After removing the solvent by simple distillation,
the crude products were subjected to chromatographic procedures,
yielding pure (E)-2-(pyridinylvinyl)quinolines 13–17 in 40–47%.
All prepared quinoline derivatives are low molecular weight
rigid and stable molecules, easily soluble in organic solvents (Table
1). The 12 compounds have been grouped according to the C-2 sub-
1
7,18
stituent in group A which contains 2-pyridinyl quinolines 6–12
and group B which includes 2-pyridinylvinyl quinolines 13–17.
cide Concentration (MFC).
So, quinoline molecules 6, 9, 10, 13, 14, 16 and 17 were tested
again, against C. albicans ATCC 10231 and C. neoformans ATCC
32264 by using a similar microplate design than that used for
determining MIC100. The inhibition percentages displayed by each
compound at the different concentrations were calculated with the
aid of a microplate reader, as explained in material and methods.
These results were plotted in Figures. 1 and 2.
2
.2. Antifungal assays
Quinolines 6–17 were submitted to antifungal assays (Table 2).
To carry out the antifungal evaluation, concentrations of com-
pounds up to 250 g/mL were incorporated to growth media
according to the CLSI standardized procedures.
B, terbinafine, and ketoconazole were used as positive controls.
l
17,18
Amphotericin
Regarding the behavior against C. neoformans (Fig. 1), all com-
pounds but 14 inhibited 50% of fungal growth at concentrations

6
508
V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
Table 2
Minimum inhibitory concentrations and minimum fungicide concentration (MIC and MFC in
lg/mL, showed as MIC/MFC) of C-2 pyridinyl and pyridinylvinyl substituted
quinolines 6–17
Compd
Structure
Ca
Sc
Cn
Afl
Afu
Ani
Mg
Tr
Tm
6
62/250
62/250
31/125
62/125
>250
62/125
250/>250
62/62
62/62
62/62
N
N
Cl
F
7
N
>250
>250
>250
>250
62/125
62/250
>250
>250
31/125
62/62
31/125
62/62
31/125
62/62
N
8
9
N
125/250
125/250
250/>250
N
62/250
62/250
62/125
62/125
62/125
62/125
62/125
62/125
62/125
62/125
62/62
62/62
62/62
62/62
62/62
62/62
N
N
1
1
1
1
0
1
2
3
125/250
125/250
N
N
Cl
>250
>250
125/250
125/250
125/>250
>250
>250
>250
>250
>250
125/125
31/62
125/125
31/62
125/125
62/125
N
N
>250
>250
>250
>250
N
N
Cl
N
F
125/>250
250/>250
250/>250
250/>250
125/>250
125/>250
125/>250
N
N
1
1
4
5
250/>250
>250
250/>250
>250
125/250
>250
125/>250
250/>250
125/>250
250/>250
125/>250
>250
62/250
62/250
62/250
N
Cl
Cl
N
250/>250
250/>250
250/>250
N
1
1
6
7
62/250
62/250
62/125
125/250
125/250
125/>250
250/>250
31/125
62/125
31/125
62/125
31/125
62/125
N
N
125/>250
125/>250
125/250
250/>250
250/>250
N
N
Amphotericin B
Terbinafine
Ketoconazole
0.98
1.95
0.49
0.49
3.90
0.49
0.25
0.49
0.25
0.49
0.98
0.12
0.49
0.98
0.49
0.49
1.96
0.25
0.12
0.04
0.06
0.06
0.01
0.03
0.06
0.03
0.03
Ca: Candida albicans ATCC 10231, Sc: Saccharomyces cerevisiae ATCC 9763, Cn: Cryptococcus neoformans ATCC 32264, Afu: Aspergillus fumigatus ATCC 26934, Afl: Aspergillus
flavus ATCC 9170, Ani: Aspergillus niger ATCC 9029, Mg: Microsporum gypseum CCC 115, Tr: Trichophyton rubrum CCC 113, Tm: T. mentagrophytes ATCC 9972. CCC = CEREMIC
(
Centro de Referencia en Micologia). ATCC: American Type Culture Collection. MIC or MFC >250 lg/mL is indicative that the compound is inactive.
lower than 20
1
l
g/mL and six compounds of them (6, 9, 10, 13 and
6) inhibited 80% of the same fungus at concentrations lower than
1.2 g/mL. Quinoline derivatives 6 and 9 showed striking results,
Based on the previous results, all compounds but 14 were tested
against six clinical isolates of C. albicans and four non-albicans
Candida spp., all of them provided by CEREMIC (see Section 4) and
seven strains of C. neoformans provided by Malbrán Institute (Bue-
nos Aires). Results showed (Table 3) that C. albicans, non-albicans
Candida spp. and C. neoformans possess different sensitivities to
the selected compounds. The whole panel of clinical strains of C.
albicans are more sensitive to compounds 9 and 16 (MIC80 = 15.6–
3
l
the first one inhibiting 50% and 80% of C. neoformans at 3.9 and
5.6 g/mL respectively, and the second one inhibiting 80% of
the same fungus at 15.6 g/mL.
1
l
l
As it can be observed in Figure 2, all compounds but 14 inhib-
ited 50% of C. albicans growth, at concentrations lower than
2
0
l
g/mL, and five of them (6, 9, 13, 16 and 17) inhibited 80% of
the same fungus at concentrations lower than 31.2 g/mL. Inter-
esting enough, compounds 6, 9, 16 showed 50% inhibition at
.8 g/mL, and 80% inhibition at 15.6 g/mL against C. albicans.
31.2
pyridinyl group and no substituents on the quinoline ring.
In turn, clinical isolates of C. neoformans are also very sensitive
to 9 (MIC80 = 15.6–31.2 g/mL, MIC50 = 7.8–31.2 g/mL) and 16
lg/mL, MIC50 = 7.8–15.6 lg/mL), which both possess a c-
l
7
l
l
l
l

V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
6509
1
00
100
80
8
6
4
2
0
0
0
0
0
60
6
9
1
1
1
16
1
6
9
10
13
40
0
3
4
1
4
20
0
7
16
1
7
0
20
40
60
80
100
120
0
20
40
60
80
100
120
Concentration (μg/mL)
Concentration (μg/mL)
Figure 1. Percentages of inhibition of Cryptococcus neoformans ATCC 32264,
produced by C-2 pyridinyl and pyridinyl-vinyl substituted quinolines 6, 9, 10, 13,
Figure 2. Percentages of inhibition of Candida albicans ATCC 10231, produced by C-
2 pyridinyl and pyridinyl-vinyl substituted quinolines 6, 9, 10, 13, 14, 16 and 17 at
different concentrations.
1
4, 16 and 17 at different concentrations.
Table 3
0% and 50% Minimum Inhibitory Concentrations (MIC80 and MIC50) of quinoline derivatives 6, 9, 10, 13, 16 and 17 against six C. albicans, four non-albicans Candida and six
8
Cryptococcus neoformans clinical isolated strains
6
9
10
13
16
17
Amph. B
Strain
C. albicans
C. albicans
C. albicans
C. albicans
C. albicans
C. albicans
C. albicans
Voucher specimen
ATCC 10231
CCC 125
CCC 126
CCC 127
CCC 128
CCC 129
CCC 130
CCC 115
CCC 124
CCC 117
CCC 131
ATCC 32264
IM 983040
IM 972724
IM 042074
IM 983036
IM 00319
IM 972751
MIC80
15.6
125
31.2
62.5
62.5
62.5
62.5
62.5
31.2
62.5
31.2
15.6
7.8
MIC50
7.8
MIC80
15.6
15.6
31.2
15.6
15.6
15.6
31.2
15.6
31.2
62.5
31.2
15.6
31.2
31.2
31.2
31.2
31.2
31.2
MIC50
7.8
15.6
15.6
7.8
MIC80
31.25
125
62.5
125
125
125
125
15.6
31.2
62.5
125
31.2
31.2
31.2
31.2
62.5
31.2
31.2
MIC50
15.6
31.2
31.2
31.2
31.2
62.5
62.5
7.8
MIC80
31.2
31.25
62.5
62.5
62.5
62.5
31.25
31.2
15.6
31.2
125
31.2
62.5
62.5
62.5
62.5
62.5
31.2
MIC50
15.6
15.6
62.5
31.2
31.2
31.2
15.6
15.6
7.8
15.6
62.5
15.6
31.2
31.2
15.6
31.2
15.6
15.6
MIC80
15.6
15.6
31.2
15.6
15.6
31.2
15.6
62.5
31.2
31.2
62.5
31.2
31.2
31.2
31.2
31.2
31.2
31.2
MIC50
7.8
7.8
15.6
15.6
7.8
15.6
7.8
31.2
7.8
15.6
31.2
15.6
7.8
MIC80
31.2
125
62.5
62.5
125
62.5
62.5
>250
>250
>250
125
31.2
62.5
62.5
62.5
62.5
62.5
31.2
MIC50
15.6
31.2
31.2
31.2
62.5
31.2
31.2
>250
>250
>250
31.2
15.6
15.6
31.2
15.6
7.8
MIC80
1.00
0.78
1.56
0.78
1.56
0.78
0.50
0.39
0.78
0.39
0.50
0.25
0.13
0.06
0.25
0.13
0.25
0.25
62.5
15.6
62.5
31.2
31.2
31.2
62.5
15.6
31.2
15.6
3.9
3.9
3.9
3.9
3.9
7.8
3.9
7.8
7.8
15.6
15.6
15.6
31.2
15.6
15.6
15.6
31.2
15.6
7.8
C. glabrata
C. parapsilopsis
C. krusei
7.8
31.2
15.6
7.8
C. tropicalis
C. neoformans
C. neoformans
C. neoformans
C. neoformans
C. neoformans
C. neoformans
C. neoformans
7.8
7.8
7.8
7.8
15.6
15.6
15.6
15.6
31.2
15.6
7.8
7.8
3.9
7.8
7.8
31.2
7.8
31.2
15.6
3.9
MIC80 and MIC50: concentration of a compound that induced 80% or 50% reduction of the growth control respectively. ATCC = American Type Culture Collection (Illinois, USA);
CCC = Center of Mycological Reference (Rosario, Argentina), IM = Malbran Institute (Buenos Aires, Argentina). C. albicans = Candida albicans; C. glabrata = Candida glabrata; C.
parapsilopsis = Candida parapsilopsis; C. krusei = Candida krusei; C. tropicalis = Candida tropicalis; C. neoformans = Cryptococcus neoformans. Amph B = Amphotericin B.
For the sake of comparison, MIC80 and MIC50 of all compounds against an ATCC standardized strain of C. albicans and C. neoformans are included.
(
MIC80 = 31.2
sensitive to 6 (MIC80 = 7.8–15.6
which possesses two important differences with 9 and 16: it pos-
sesses a -pyridinyl moiety on C-2 and an ethyl substituent on
l
g/mL, MIC50 = 3.9–15.6
l
g/mL), but they are more
clinically important fungi C. albicans and non-albicans Candida spe-
cies. In turn, 6-ethyl-2-(pyridin-2-yl)quinoline 6 showed the best
properties against standardized as well as clinical strains of C.
neoformans.
l
g/mL, MIC50 = 3.9–7.8
lg/mL),
a
the quinoline ring.
It is important to take into account that one of the strategies for
avoiding antifungal resistance is the treatment of fungal infections
with the appropriate antifungal agent when the ethiological agent
is known. As a consequence, our findings could open an avenue for
the development of antifungal agents which inhibits either C. albi-
cans or C. neoformans which, as stated above, are clinically impor-
tant fungi for which new inhibitory structures are welcome.
These results are not uncommon since some antifungal drugs
have demonstrated selectivity for one type of fungi, such as the
case of terbinafine which has activity mainly on dermatophytes,
which are mainly used to treat esophageal candidiasis and invasive
aspergilloses, refractory to other antifungal drugs.
3
. Conclusion
4
. Experimental
We report here the synthesis and antifungal properties of a ser-
ies C-2 pyridinyl and pyridinylvinyl substituted quinolines acting
as antifungal agents. All members of the series showed activities
against dermatophytes and some of them possessed a broad spec-
trum of action. 2-(Pyridin-4-yl)quinoline 9 and 2-(2-pyridin-4-yl)
vinyl)quinoline 16 showed the best MIC80 and MIC50 against the
4.1. Chemistry
The melting points (uncorrected) were determined on a Fisher–
Johns melting point apparatus. The IR spectra were recorded on a
Lumex infralum FT-02 spectrophotometer in KBr. H NMR and
1

6
510
V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
13CNMR spectra were recorded on Bruker AC-200 or Bruker AC-400
spectrometers. Chemical shifts are reported in ppm (d) relative to
dd, J = 6.1, 1.0 Hz, 3 -HPy and 5 -HPy), 8.22 (1H, d, J = 8.6 Hz, 3-H),
0
0
0
8.15 (1H, d, J = 8.6 Hz, 8-H), 8.05 (2H, each dd, J = 6.4, 1.0 Hz, 2 -
Py and 6 -HPy), 7.85 (1H, d, J = 7.0 Hz, 4-H), 7.81 (1H, d,
0
the solvent peak (CHCl
3
in CDCl
3
at 7.24 ppm for protons). Signals
H
are designated as follows: s, singlet; d, doublet; dd, doublet of dou-
blets; ddd, doublet of doublets of doublets; t, triplet; td, triplet of
doublets; q, quartet; m, multiplet; br., broad. A Hewlett–Packard
J = 8.2 Hz, 5-H), 7.74 (1H, ddd, J = 7.8, 7.8, 1.4 Hz, 6-H), 7.54 (1H,
1
3
ddd, J = 7.2, 7.2, 2.1 Hz, 7-H);
3
C NMR (50.3 MHz, CDCl ): d
154.4, 150.5 (2C), 148.3, 146.6, 137.3, 130.1, 129.9, 127.7, 127.6,
+ꢀ
5
890a series II Gas Chromatograph interfaced to an HP 5972 mass
127.3, 121.6 (2C), 118.4; GC–MS: t
Anal. Calcd for C14 : C, 81.53; H, 4.89; N, 13.58. Found: C,
81.54; H, 4.87; N, 13.59.
R
: 21.26 min, m/z: 206 (M ).
selective detector (MSD) with an HP MS Chemstation Data system
was used for MS identification at 70 eV using a 60 m capillary col-
umn coated with HP-5 [5%-phenyl-poly(dimethyl-siloxane)]. Ele-
mental analyses were performed on a Perkin–Elmer 2400 Series
II analyzer, and were within ±0.4 of theoretical values. The reaction
progress was monitored using thin layer chromatography on a
silufol UV254 TLC aluminum sheet.
10 2
H N
4.1.1.5. 6-Methyl-2-(pyridin-4-yl)quinoline (10).
lid; Yield 42%; mp 82–84 °C; H NMR (200 MHz, CDCl ): d 8.69
Brown so-
1
3
0
0
(2H, each dd, J = 6.1, 1.0 Hz, 3 -HPy and 5 -HPy), 8.07 (1H, d,
J = 8.2 Hz, 3-H), 8.00 (1H, d, J = 7.0 Hz, 8-H), 7.98 (2H, each dd,
0
0
J = 6.1, 1.1 Hz, 2 -HPy and 6 -HPy), 7.74 (1H, d, J = 8.2 Hz, 4-H),
7.52 (1H, d, J = 6.5 Hz, 7-H), 7.51 (1H, br s, 5-H), 2.49 (3-H, s, 6-
4
6
.1.1. General procedure for synthesis of 2-pyridinylquinolines
–12
1
3
CH
146.7, 137.3, 136.6, 132.4, 129.6, 127.9, 126.4, 121.5 (2C), 118.4,
21.7. Anal. Calcd for C15 : C, 81.79; H, 5.49; N, 12.72. Found
C, 81.78; H, 5.87; N, 12.73.
3 3
); C NMR (50.3 MHz, CDCl ): d 153.4, 150.4 (2C), 146.8,
To a solution of the appropriate aniline (1.00 mmol) and pyri-
dinecarboxaldehyde (1 mmol) in anhydrous CH
3
CN (15 mL) under
12 2
H N
N
2
, 20 mol % BiCl was added, and to the resulting mixture was
3
added ethyl vinyl ether (4.0 mmol). The reaction mixture was stir-
red at gentle reflux for 6 h and then quenched with a solution of
4.1.1.6. 6-Chloro-2-(pyridin-4-yl)quinoline (11).
Brown so-
1
Na
2
CO
3
. The organic layer was separated, and dried with Na
2
SO
4
.
lid; Yield 33%, mp 138–140 °C; H NMR (200 MHz, CDCl ): d 8.77
3
0
0
The organic solvent was removed in vacuo, the crude which were
separated by chromatography column to afford the respective
(2H, each dd, J = 6.1, 1.8 Hz, 3 -HPy and 5 -HPy), 8.19 (1H, d,
J = 8.6 Hz, 3-H), 8.11 (1H, d, J = 7.1 Hz, 8-H), 8.05 (2H, each dd,
0
0
2
-pyridinylquinolines 3–10.
J = 4.3, 1.4 Hz, 2 -HPy and 6 -HPy), 7.91 (1H, d, J = 8.6 Hz, 4-H),
.83 (1H, d, J = 2.2 Hz, 5-H), 7.68 (1H, dd, J = 8.9, 2.2 Hz, 7-H); 13
NMR (50.3 MHz, CDCl ): d 154.7, 150.6 (2C), 148.0, 146.2, 136.4,
7
C
4
.1.1.1. 6-Ethyl-2-(pyridin-2-yl)quinoline (6).
Brown solid.
): d 8.72 (1H,
3
1
mp 148–150 °C; Yield 32%; H NMR (200 MHz, CDCl
d, J = 4.6 Hz, 3 -HPy), 8.64–8.60 (1H, m, 4 -HPy), 8.51 (1H, d,
3
133.0, 131.6, 131.1, 128.4, 126.3, 121.6 (2C), 119.3; GC–MS: t
R
:
0
0
+ꢀ
23.28 min, m/z: 240 (M ). Anal. Calcd for C14
H
9
ClN
2
: C, 69.86; H,
J = 8.6 Hz, 3H), 8.21 (1H, d, J = 8.6 Hz, 8H), 8.09 (1H, d, J = 8.6 Hz,
3.77; N, 11.64. Found: C, 69.85; H, 3.77; N, 11.64.
0
4
7
H), 7.83 (1H, ddd, J = 7.8, 7.8, 1.7 Hz, 5 -Hpy), 7.62 (1H, br s, 5H),
0
.60 (1H, dd, J = 7.9, 2.2 Hz, 7H), 7.26–7.32 (1H, m, 6 -HPy), 2.84
4.1.1.7. 8-Chloro-2-(pyridin-4-yl)quinoline (12).
Brown so-
1
3
1
(
2H, q, J = 7.8 Hz, 6-CH
2
CH
3
), 1.34 (3H, t, J = 7.5 Hz, 6-CH
CH
2 3
);
C
lid; Yield 25%; mp 176–178 °C; H NMR (200 MHz, CDCl
3
): d 8.86
0
3
NMR (50.3 MHz, CDCl ): d 142.9, 136.9, 136.4, 133.7, 130.9, 129.6,
(1H, d, J = 6.1 Hz, 3-H), 8.75 (2H, each dd, J = 4.3, 1.4 Hz, 3 -HPy
0
0
0
1
28.4, 128.0, 125.2, 123.9, 122.3, 121.8, 120.4, 118.9, 34.9, 15.4;
and 5 -HPy), 7.76 (2H, each dd, J = 4.3, 2.2 Hz, 2 -HPy and 6 -HPy),
7.68 (1H, d, J = 6.1 Hz, 4-H), 7.44 (1H, dd, J = 7.5, 1.4 Hz, 7-H),
7.23 (1H, dd, J = 9.0, 7.2 Hz, 6-H), 7.00 (1H, dd, J = 7.5, 1.7 Hz, 5-
+ꢀ
GC–MS: t
R
: 22.71 min, m/z: 234 (M ). Anal. Calcd for C16
14 2
H N : C,
8
2.02; H, 6.02; N, 11.96. Found: C, 82.03; H, 6.00; N, 11.94.
1
3
H); C NMR (100 MHz, CDCl
3
): d 152.9, 151.5 (2C), 150.0, 140.0,
4
.1.1.2. 6-Chloro-2-(pyridin-3-yl)quinoline (7).
Brown solid;
): d 9.34 (1H,
130.5, 130.0, 127.8, 127.5, 126.4, 125.9, 123.2, 120.1 (2C); GC–
1
+.
Yield 36%; mp 150-152 °C; H NMR (200 MHz, CDCl
d, J = 2.5 Hz, 2 -HPy), 8.70 (1H, dd, J = 4.8, 1.4 Hz, 4 -HPy), 8.48 (1H,
dt, J = 7.8, 1.8 Hz, 5 -HPy), 8.18 (1H, d, J = 8.6 Hz, 3-H), 8.10 (1H, d,
3
R 9 2
MS: t : 19.75 min, m/z: 216 (M ). Anal. Calcd for C14H ClN : C,
0
0
69.86; H, 3.77; N, 11.64. Found: C, 69.87; H, 3.76; N, 11.64.
0
J = 8.9 Hz, 8-H), 7.90 (1H, d, J = 8.2 Hz, 4-H), 7.83 (1H, d,
J = 2.1 Hz, 5-H), 7.68 (1H, dd, J = 8.9, 2.5 Hz, 7-H), 7.46 (1H, ddd,
4.1.2. General procedure for synthesis of (E)-2-(2-(pyridinyl)-
vinyl) quinolines 13–17
0
13
J = 7.9, 4.6, 0.7 Hz, 6 -HPy); C NMR (50.3 MHz, CDCl
3
): d 154.9,
The quinaldines 5 (1.0 mmol) were solubilized in the presence
1
1
50.5, 148.8, 146.8, 136.3, 134.9, 134.7, 132.6, 131.4, 131.0,
of acetic anhydride were then added a,b,c-pyridincarboxaldehyde
+
ꢀ
27.9, 126.3, 123.8, 119.4; GC–MS: t
ClN : C, 69.86; H, 3.77; N, 11.64. Found: C,
9.89; H, 3.75; N, 11.65.
R
: 27.03 min, m/z: 240 (M ).
3 (1.00 mmol), the reaction mixture was stirred at gentle reflux for
12 h. The reaction mass was subjected to simple distillation,
removing the solvent, the products obtained were purified by col-
umn chromatography on silica gel with gradual increase in polarity
by using mixtures of solvents (hexane/ethyl acetate) as eluents.
Anal. Calcd for C14
6
H
9
2
4
.1.1.3. 6-Fluoro-2-(pyridin-3-yl)quinoline (8).
Brown solid;
): d 9.32 (1H,
1
Yield 23%; mp 162–164 °C; H NMR (200 MHz, CDCl
d, J = 2.5 Hz, 2 -HPy), 8.69 (1H, dd, J = 4.6, 1.7 Hz, 4 -HPy), 8.47 (1H,
dt, J = 7.8, 1.8 Hz, 5 -HPy), 8.19 (1H, d, J = 8.6 Hz, 3-H), 8.15
3
0
0
4.1.2.1.
(13).
(E)-6-Fluoro-2-(2-(pyridin-2-yl)vinyl)quinoline
0
1
3
Red oil; Yield 37%; H NMR (200 MHz, CDCl ): d 8.72
0
0
(
7
1H, dd, J = 9.3, 5.3 Hz, 5-H), 7.52 (1H, dd, J = 8.6, 2.0 Hz, 8-H),
.88 (1H, d, J = 8.2 Hz, 4-H), 7.47-7.41 (1H, m, 7-H), 7.47-7.41
(1H, d, J = 4.6 Hz, 3 -HPy), 8.60-8.64 (1H, m, 4 -HPy), 8.26 (1H, ddd,
J = 7.2, 7.2, 1.4 Hz, 7-H), 8.19 (1H, d, J = 8.6 Hz, 3-H), 8.15 (1H, dd,
J = 9.3, 5.3 Hz, 8-H), 7.83 (1H, ddd, J = 7.8, 7.8, 1.7 Hz, 5 -HPy),
1
3
0
(
1H, m, 6’-HPy);
J
C
NMR (100 MHz, CDCl
3
):
d
160.6 (d,
1
C,F = ꢀ248.1 Hz), 154.0, 150.5, 150.3, 148.7, 145.5, 136.5, 134.8,
7.88 (1H, d, J = 8.2 Hz, 4-H), 7.52 (1H, dd, J = 8.6, 4.7 Hz, 5-H),
3
2
1
32.3 (d,
J
C,F = 9.0 Hz), 128.0, 123.7, 120.3 (d,
J
C,F = 25.7 Hz),
: 22.68 min, m/z: 224
: C, 74.99; H, 4.05; F, 8.47; N,
: C, 74.96; H, 4.03; N, 12.48.
7.26-7.32 (1H, m, 6’-HPy), 7.23 (1H, d, J = 20.9 Hz, H
a
), 7.21 (1H, d,
158.2. (d,
JC,F = 260.1 Hz), 157.0, 150.1, 149.4, 146.5, 136.4, 131.3 (2C),
2
13
1
19.2, 110.6 (d,
J
C,F = 23.0 Hz); GC–MS: t
R
J = 24.4 Hz,
b
H );
3
C NMR (100 MHz, CDCl ): d
+ꢀ
1
(
M ). Anal. Calcd for C14
9
H FN
2
3
1
2.49. Found: C14
H FN
9 2
130.0 (d, JC,F = 7.2 Hz), 129.3, 125.6, 123.0, 122.8, 122.5, 122.0 (d,
2
2
J
C,F = 28.4 Hz), 120.7 (d,
J
C,F = 27.0 Hz); GC–MS: t
R
: 30.71 min,
.1.1.4. 2-(Pyridin-4-yl)quinoline (9) 7
.
Brown solid; Yield
): d 8.75 (2H, each
m/z: 250 (M ). Anal. Calcd for C16
+ꢀ
H
11FN : C, 76.79; H, 4.43; F,
4
2
1
2
2%; mp 148–150 °C; H NMR (200 MHz, CDCl
3
7.59; N, 11.19. Found: C, 76.78; H, 4.42; F, 7.59; N, 11.20.

V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
6511
4
.1.2.2. (E)-2-(2-(Pyridin-3-yl)vinyl)quinoline (14).
Green
Buenos Aires)]. The isolates included 10 strains of Candida spp.
(6 of them of C. albicans and 4 of C. non-albicans) and 6 strains
of Cryptococcus neoformans. The number of voucher specimens
is showed in Table 3. Strains were grown on Sabouraud-chloram-
phenicol agar slants for 48 h at 30 °C, maintained on slopes of
Sabouraud-Dextrose agar (SDA, Oxoid) and sub-cultured every
15 days to prevent pleomorphic transformations. Inocula of cell
or spore suspensions were obtained according to reported proce-
1
solid; Yield 35%; mp 173–175 °C; H NMR (200 MHz, CDCl ): d
8
8
td, J = 5.4, 3.5 Hz, 5 -HPy), 7.77 (1H, dd, J = 8.0, 1.4 Hz, 8-H), 7.76-
7
J = 7.9, 7.9, 1.0 Hz, 6-H), 7.38 (1H, d, J = 16.0 Hz, H
J = 7.9 Hz, 5-H), 7.30 (1H, d, J = 23.3 Hz, H
CDCl
3
0
0
.82 (1H, d, J = 2.2 Hz, 2 -HPy), 8.53 (1H, dd, J = 4.6, 2.0 Hz, 4 -HPy),
.14 (1H, d, J = 8.9 Hz, 3-H), 8.10 (1H, d, J = 8.9 Hz, 4-H), 8.0 (1H,
0
0
.71 (1H, m, 7-H), 7.66–7.59 (1H, m, 6 -HPy), 7.50 (1H, ddd,
a
), 7.33 (1H, d,
); C NMR (50.3 MHz,
): d 154.7, 148.7, 148.6, 147.8, 136.2, 133.2, 132.0, 130.6,
30.0, 129.6, 128.9, 127.4, 127.2, 126.2, 123.5, 119.1; GC–MS: t
13
b
3
3
dures and adjusted to 1–5 ꢂ 10 cells/spores with colony forming
1
7,18
1
2
5
R
:
units (CFU) /mL.
+ꢀ
7.43 min, m/z: 232 (M ). Anal. Calcd for C16
12 2
H N : C, 82.73; H,
.21; N, 12.06. Found: C, 82.74; H, 5.22; N, 12.03.
4.2.2. Antifungal susceptibility testing
Minimum Inhibitory Concentration (MIC) of each extract or
compound was determined by using broth microdilution tech-
niques according to the guidelines of the National Committee for
4
.1.2.3.
(E)-6-Chloro-2-(2-(pyridin-3-yl)vinyl)quinoline
1
(
15).
Beige solid; Yield 39%; mp 177–179 °C;
H NMR
0
17
(
200 MHz, CDCl
3
0
): d 8.80 (1H, d, J = 2.2 Hz, 2 -HPy), 8.52 (1H, dd,
Clinical Laboratory Standards for yeasts (M27-A3) and for fila-
18
J = 5.2, 1.8 Hz, 4 -HPy), 8.02 (1H, d, J = 7.9 Hz, 3-H), 7.97 (1H, d,
J = 8.6 Hz, 4-H), 7.90 (1H, td, J = 7.9, 1.8 Hz, 5 -HPy), 7.72 (1H, d,
J = 8.2 Hz, 8-H), 7.73 (1H, bs, 5-H), 7.63–7.59 (1H, m, 7-H), 7.35
mentous fungi (M 38-A2).
MIC values were determined in
0
RPMI-1640 (Sigma, St. Louis, Mo, USA) buffered to pH 7.0 with
MOPS. Microtiter trays were incubated at 30 °C for yeasts and spe-
cies of Aspergillus and at 28–30 °C for dermatophytes in a moist,
dark chamber. MICs were visually recorded at 48 h for yeasts,
and at a time according to the control fungus growth, for the rest
of fungi.
0
(
1H, d, J = 22.2 Hz, H
a
), 7.32–7.26 (1H, m, 6 -HPy), 7.29 (1H, d,
1
3
J = 22.3 Hz, H
1
1
b
);
3
C NMR (50.3 MHz, CDCl ): d 159.6, 155.4,
49.6, 149.3, 147.9, 146.6, 136.2, 133.3, 132.0, 131.0, 130.9,
30.4, 128.0, 126.3, 123.7, 120.4; GC–MS: t : 24.88 min, m/z: 265
: C, 72.05; H, 4.16; N, 10.50. Found:
R
+ꢁ
(
M ). Anal. Calcd for C16
H
11ClN
2
For the assay, stock solutions of pure compounds were twofold
C, 72.06; H, 4.17; N, 10.51.
diluted with RPMI from 250–0.98
lg/mL (final volume = 100
ll)
and a final DMSO concentration 61%. A volume of 100
l
l of inocu-
4
.1.2.4. (E)-2-(2-(Pyridin-4-yl)vinyl)quinoline (16).
Green
solid; Yield 43%; mp 169–172 °C; H NMR (200 MHz, CDCl ): d
.52 (2H, d, J = 6.1 Hz, 3 -HPy and 5 -HPy), 8.02 (2H, each d,
lum suspension was added to each well with the exception of the
sterility control where sterile water was added to the well instead.
Amphotericin B, Terbinafine and Ketoconazole were used as posi-
tive controls.
1
3
0
0
8
0
0
J = 8.2 Hz, 2 -HPy and 6 -HPy), 7.67 (1H, d, J = 8.0 Hz, 3-H), 7.65
1H, d, J = 7.2 Hz, 8-H), 7.61 (1H, d, J = 7.4 Hz, 5-H), 7.52 (1H, d,
J = 8.2 Hz, 4-H), 7.44 (1H, d, J = 18.0 Hz, H ), 7.42–7.37 (1H, m, 6-
H), 7.42–7.37 (1H, m, 7-H), 7.41 (1H, d, J = 17.2 Hz, H
(
Endpoints recorded in Table 2 were defined as the lowest con-
centration of drug resulting in total inhibition (MIC100) of visual
growth compared to the growth in the control wells containing
a
1
3
b
); C NMR
): d 174.7, 154.4, 148.9 (2C), 147.8, 144.9, 136.9,
33.7, 131.2, 130.2, 129.0, 127.6, 126.9, 121.7 (2C), 119.4; GC–
(
1
50.3 MHz, CDCl
3
no antifungal. Compounds with MICs >250
inactive.
lg/mL were considered
+
MS: t
8
R
: 27.07 min, m/z: 249 (M ꢀ). Anal. Calcd for: C16
H
12
N
2
: C,
2.73; H, 5.21; N, 12.06. Found C, 82.74; H, 5.20; N, 12.04.
4.2.3. MFC determination
The minimum fungicidal concentration (MFC) of each com-
pound against each isolate was also determined as follows: After
determining the MIC, an aliquot of 5 lL sample was withdrawn
from each clear well of the microtiter tray and plated onto a
150 mm RPMI-1640 agar plate buffered with MOPS (Remel, Le-
nexa, Kans.). Inoculated plates were incubated at 30 °C, and MFCs
were recorded after 48 h. The MFC was defined as the lowest con-
centration of each compound that resulted in total inhibition of
visible growth.
4
.1.2.5. (E)-6-Chloro-2-(2-(pyridin-4-yl)vinyl)quinoline
1
(
17).
Green solid; yield 40%; mp 175–177 °C;
H
NMR
0
(
200 MHz, CDCl
3
): d 8.78 (2H, each dd, J = 6.0, 4.2 Hz, H-3 Py and
0
0
0
H-5 Py), 8.65 (1H, dd, J = 6.1, 4.3 Hz, H-2 py and H-6 py), 8.10 (1H,
d, J = 9.3 Hz, 3-H), 8.10 (1H, d, J = 9.3 Hz, 4-H), 7.90 (1H, d, J
=
7.9 Hz, 8-H), 7.79 (1H, d, J = 2.5 Hz, 5-H), 7.68 (1H, dd, J = 8.3,
1
H
.0 Hz, 7-H), 7.56 (1H, d, J = 21.5 Hz, H
a
), 7.53 (1H, d, J = 16.9 Hz,
1
3
b
); C NMR (100 MHz, CDCl ): d 152.5, 150.0 (2C), 145.9, 145.4,
3
1
33.4, 133.0, 132.5, 130.0, 129.4 (2C), 126.8, 125.9, 123.0, 121.2
ꢀ
(
2C); GC–MS: t
R
: 27.09 min, m/z: 266 (M+ ). Anal. Calcd for:
4.2.4. Inhibition percentage determination
C
16
H
11ClN
2
: C, 72.05; H, 4.16; N, 10.50. Found: C, 72.04; H, 4.17;
The test was performed in 96-well microplates. Compound test
wells (CTWs) were prepared with stock solutions of each quinoline
derivative in DMSO (maximum concentration 61%), diluted with
N, 10.51.
4
4
.2. Biology
RPMI-1640 to final concentrations 250–0.98
pension (100 l) was added to each well (final volume in the
well = 200 l). A growth control well (GCW) (containing medium,
lg/mL. Inoculum sus-
l
.2.1. Microorganisms and media
l
For the antifungal evaluation, standardized strains from the
inoculum, the same amount of DMSO used in CTW, but com-
pound-free) and a sterility control well (SCW) (sample, medium
and sterile water instead of inoculum) were included for each fun-
gus tested. Microtiter trays were incubated in a moist, dark cham-
ber at 30 °C, 24 or 48 h for C. albicans or C. neoformans, respectively.
Microplates were read in a VERSA Max microplate reader (Molec-
ular Devices, Sunnyvale, CA, USA). Amphotericin B was used as po-
sitive control.
American Type Culture Collection (ATCC), Rockville, MD, USA,
and CEREMIC (CCC), Centro de Referencia en Micología, Facultad
de Ciencias Bioquímicas y Farmacéuticas, Suipacha 531-(2000)-
Rosario, Argentina were used in a first instance of screening: Can-
dida albicans ATCC 10231, Saccharomyces cerevisiae ATCC 9763,
Cryptococcus neoformans ATCC 32264, Aspergillus flavus ATCC
9
170, A. fumigatus ATTC 26934, A. niger ATCC 9029, Trichophyton
rubrum CCC 110, T. mentagrophytes ATCC 9972 and M. gypseum
CCC 115.
Active compounds were tested against clinical isolates from
CEREMIC and Malbrán Institute [(M), Av. Velez Sarsfield 563.
Tests were performed in duplicate. Reduction of growth for
each compound concentration was calculated as follows: % of inhi-
bition = 100 ꢀ (OD405 CTW ꢀ OD405 SCW)/(OD405 GCW ꢀ OD405
SCW).

6
512
V. V. Kouznetsov et al. / Bioorg. Med. Chem. 20 (2012) 6506–6512
7. Meléndez Gómez, C. M.; Kouznetsov, V. V.; Sortino, M.; Álvarez, S.; Zacchino, S.
4
.2.5. MIC80 and MIC50 determination
MIC80 and MIC50 were defined as the lowest concentration of a
Bioorg. Med. Chem. 2008, 16, 7908.
8
9
.
.
Vargas, M. L. Y.; Castelli, M. V.; Kouznetsov, V.; Urbina, G. J. M.; López, S. N.;
Sortino, M.; Enriz, R. D.; Ribas, J. C.; Zacchino, S. Bioorg. Med. Chem. 2003, 11,
1531.
Musiol, R.; Jampilek, J.; Kralova, K.; Richardson, D. R.; Kalinowski, D.; Podeszwa,
B.; Finster, J.; Niedbala, H.; Palka, A.; Polanski, J. Bioorg. Med. Chem. 2007, 15,
compound that showed 80% or 50% reduction of the growth control
respectively and was determined from the results obtained in the
Inhibition percentage determination.
1280.
Acknowledgments
10. Kouznetsov, V. V.; Meléndez Gómez, C. M.; Luna Parada, L. K.; Bermúdez, J. H.;
Vargas Méndez, L. Y.; Muñoz Acevedo, A. Mol. Divers. 2011, 1007, 15.
1
1. Fournet, A.; Barrios, A. A.; Muñoz, V.; Hocquemiller, R.; Cavé, A.; Bruneton, J. J.
V.V.K. thanks DIEF-UIS (Grant No. 5176), C.M.M.G. acknowledges
COLCIENCIAS for the fellowship, S.A.Z. acknowledges ANPCyT
PICT 0608. L.S. and M.G.D. acknowledge CONICET for fellowships.
Antimicrob. Agents. Chemother. 1993, 37, 859.
12. Fournet, A.; Barrios, A. A.; Muñoz, V.; Hocquemiller, R.; Roblot, F.; Cavé, A.;
Richomme, P.; Bruneton, J. Phytother. Res. 1994, 8, 174.
13. Fakhfakh, M. A.; Franck, X.; Fournet, A.; Hocquemiller, R.; Figadere, B.
Tetrahedron Lett. 2001, 42, 3847.
Supplementary data
14. Muscia, G. C.; Bollini, M.; Carnevale, J. P.; Bruno, A. M.; Asís, S. E. Tetrahedron
Lett. 2006, 47, 8811.
1
5. Blackie, M. A. L.; Beagley, P.; Croft, S. L.; Kendrick, H.; Moss, J. R.; Chibale, K.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmc.2012.08.036.
Bioorg. Med. Chem. 2007, 15, 6510.
16. Gómez-Barrio, A.; Montero-Pereira, D.; Nogal-Ruiz, J. J.; Escario, J. A.; Muelas-
Serrano, S.; Kouznetsov, V. V.; Vargas Méndez, L. Y.; Urbina González, J. M.;
Ochoa, C. Acta Parasitol. 2006, 51, 73.
References and notes
1
7. CLSI, Clinical and Laboratory Standards Institute (formerly NCCLS, National
Committee for Clinical and Laboratory Standards). Method M27–A3, 3rd ed.;
Wayne, Ed.; NCCLS: Pennsylvania, 2008; Vol. 28 (14), pp 1–25.
1.
2.
3.
4.
Mathew, B.; Nath, M. ChemMedChem. 2009, 4, 310.
Brown, E.; Wright, G. Chem. Rev. 2005, 105, 759.
Chen, S.; Playford, E.; Sorrell, T. Curr. Opin. Pharmacol. 2010, 10, 522.
Mukherjee, P.; Leidich, S.; Isham, N.; Leitner, I.; Ryder, N.; Ghannoum, M.
Antimicrob. Agents Chemother. 2003, 47, 82.
18. CLSI, Clinical and Laboratory Standards Institute (formerly NCCLS, National
Committee for Clinical and Laboratory Standards). Method M-38-A2, 2nd ed.;
Wayne, Ed.; NCCLS: Pennsylvania, 2008; Vol. 28 (16), pp 1–35.
19. Kontoyannis, D.; Mantadakis, E.; Samonis, G. J. Hosp. Inf. 2003, 53, 243.
20. Singh, N. Lancet Infect. Dis. 2003, 3, 703.
5
6
.
.
Vicente, M. F.; Basilio, A.; Cabello, A.; Peláez, F. Clin. Microbiol. Infect. 2003, 9, 15.
Musiol, R.; Jampilek, J.; Buchta, V.; Silva, L.; Niedbala, H.; Podeszwa, B.; Palka,
A.; Majerz-Maniecka, K.; Oleksyn, B.; Polanski, J. Bioorg. Med. Chem. 2006, 14,
21. Pfaller, M. A.; Diekema, D. Clin. Microbiol. Rev. 2007, 20, 133.
3
592.